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PossibleAPI.md

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API

ERC223 requires contract to implement the ERC223Receiver interface in order to receive tokens. If a user tries to send ERC223 tokens to a non-receiver contract the function will throw in the same way that it would if you sent ether to a contract without the called function being payable.

An example of the high-level API for a receiver contract is:

contract ExampleReceiver is StandardReceiver {
  function foo() tokenPayable {
    LogTokenPayable(tkn.addr, tkn.sender, tkn.value);
  }

  function () tokenPayable {
    LogTokenPayable(tkn.addr, tkn.sender, tkn.value);
  }

  event LogTokenPayable(address token, address sender, uint value);
}

Where functions that have the tokenPayable can only be called via a token fallback and inside the functions you have access to the tkn struct that tries to mimic the msg struct used for ether calls.

The function foo() will be called when a user transfers ERC223 tokens to the receiver address.

  // 0xc2985578 is the identifier for function foo. Sending it in the data parameter of a tx will result in the function being called.

  erc223.transfer(receiverAddress, 10, 0xc2985578)

What happens under the hood is that the ERC223 token will detect it is sending tokens to a contract address, and after setting the correct balances it will call the tokenReceived function on the receiver with the specified data. StandardReceiver will set the correct values for the tkn variables and then perform a delegatecall to itself with the specified data, this will result in the call to the desired function in the contract.

The current tkn values are:

  • tkn.sender the original msg.sender to the token contract, the address originating the token transfer.

    • For user originated transfers sender will be equal to tx.origin
    • For contract originated transfers, tx.origin will be the user that made the transaction to that contract.

  • tkn.origin the origin address from whose balance the tokens are sent

    • For transfer(), it will be the same as tkn.sender
    • For transferFrom(), it will be the address that created the allowance in the token contract

  • tkn.value the amount of tokens sent

  • tkn.data arbitrary data sent with the token transfer. Simulates ether tx.data.

  • tkn.sig the first 4 bytes of tx.data that determine what function is called.